It is relatively common for radiotelephone handsets to include internal patch antenna arrangements, since these are relatively inexpensive to manufacture and since they can have suitably narrow bandwidths at desired operating frequencies. However, the use of patch antennas presents a problem when the radiotelephone is required to operate in more than two multiple frequency bands, for example in the PCS and DCS bands as well as the GSM 900 band. The PCS band comprises the frequencies 1850 to 1990 MHz, and the DCS transmitter band comprises the frequencies 1710 to 1785 MHz, the DCS receiver band comprises the frequencies 1805 to 1889 MHz.
Patch antennas which are arranged to operate multiple frequency bands are known from, for example, U.S. Pat. No. 5,777,581, which discloses a patch antenna connectable to plural tuning strips by respective switches. An antenna more suitable for use in mobile telephone applications is disclosed in JP11-136025. In this document, a ground plane and an antenna element are formed on opposite faces of a substrate. The antenna element is grounded at one end, can be coupled to ground at another end by a controllable switch. Further switches may couple other locations on the antenna element to ground potential, allowing the antenna to be tuned to plural discreet frequencies.
It is an aim of the invention to provide an improved antenna arrangement.